1. Field of the Invention
The present invention relates to a pressure-holding valve for a fuel injection system with a high-pressure region and a low-pressure region, which valve has a valve housing equipped with a first connection that can be connected to the low-pressure region and a second connection that can be connected to the return of a fuel injection valve device, which valve housing contains a reciprocating valve cup that is prestressed in opposition to the prestressing force of a first spring device and has a through opening, which can be closed by a closing element that is prestressed in opposition to the prestressing force of a second spring device in order to maintain a minimum pressure in the return. The present invention also relates to a tool for reducing the pressure in an above-described pressure-holding valve. The present invention also relates to a set including an above-described pressure-holding valve and an above-described tool. The present invention also relates to a fuel injection system that has a low-pressure region and a high-pressure region from which fuel is supplied to a fuel injection valve device that is connected to the low-pressure region via a return.
2. Description of the Prior Art
In conventional fuel injection systems, piezoelectric actuators can be used to assure a defined injection of fuel. Such a piezoelectric actuator can be coupled to a control valve element by means of a hydraulic coupling device. In order to assure a filling of the coupling device, a minimum pressure can be maintained in the return of the fuel injection valve device in the fuel injection system, even after the system itself or an associated internal combustion engine is switched off. This minimum pressure can be maintained by means of a pressure-holding valve in the return of the fuel injection valve device. The minimum pressure to be maintained by the pressure-holding valve can lead to an uncontrolled spraying of fuel during installation and/or maintenance work on the fuel injection system.
The object of the present invention is to provide a pressure-holding valve, a tool, a set, and/or a fuel injection system, which make it easily possible to selectively reduce the minimum pressure to be maintained by the pressure-holding valve.